In an electronic apparatus which includes a plurality of parallel/serial converting devices connected in cascade, and serially converts a plurality of digital signals output from a plurality of switches or sensors by the respective parallel/serial converting devices for reading, even when only some of the plurality of digital signals are desired to be read, all the parallel/serial converting devices are operated, and thus, all the digital signals are serially converted. Thus, electric power is wastefully consumed, and a reading cycle is lengthened.